US Backdoor Roth IRA Calculator
Backdoor Roth lets high earners contribute to Roth IRA despite income limits: make a non-deductible Traditional IRA contribution, then immediately convert to Roth.
US Roth Conversion Calculator
Working calculator with pro-rata rule modeling for any Traditional/Roth mix.
Open US Roth Conversion Calculator →About this tool
The backdoor Roth calculator models whether high earners can route 7,000 USD per year (8,000 USD at 50 plus) into a Roth IRA in 2026 even after their MAGI passes the 150,000 USD single or 236,000 USD MFJ phase-out start. The technique is a two step contribute-then-convert; the calculator surfaces the pro-rata trap that turns a "tax free" conversion into a partly taxable event.
How it works
Step 1: Non-deductible Traditional IRA contribution (up to 7,000 USD) Step 2: Convert to Roth (preferably within 1 to 5 days) Step 3: File Form 8606 to track basis Taxable conversion % = Pre-tax IRA balance / (Pre-tax IRA + After-tax basis) Conversion tax = Conversion x Taxable % x Marginal rate
- 2026 IRA cap: 7,000 USD under 50, 8,000 USD at 50 plus (IRS Notice 2025-79). Per spouse if both have earned income.
- Roth phase-out: direct contribution drops to zero between 150,000 to 165,000 USD MAGI single and 236,000 to 246,000 USD MFJ in 2026.
- Pro-rata aggregation: covers Traditional, SEP, and SIMPLE IRAs (not 401(k), 403(b), or your spouse's IRAs). Workplace plans are aggregated separately.
- Marginal rate: 2026 federal brackets for single filers: 22 percent above 48,475 USD; 24 percent above 103,350 USD; 32 percent above 197,300 USD; 35 percent above 250,525 USD; 37 percent above 626,350 USD.
Worked example
A 36 year old single tech worker earning 210,000 USD (32 percent federal bracket) wants to fund a Roth IRA in 2026. MAGI is 195,000 USD which is fully above the 165,000 USD phase-out ceiling, so direct Roth is zero. She already rolled an old 401(k) into a Traditional IRA five years ago with 50,000 USD now sitting in it.
- Pro-rata trap detected: the 50,000 USD pre-tax balance would taint any backdoor conversion. With a 7,000 USD non-deductible contribution, only 7,000 / 57,000 = 12.3 percent is basis; 87.7 percent of the conversion is taxable.
- Fix: roll the 50,000 USD Traditional IRA back into her current employer 401(k) (this is allowed). Workplace plans do not count for pro-rata.
- Contribute: 7,000 USD non-deductible to a fresh Traditional IRA in January 2026.
- Convert: next business day, transfer 7,000 USD from Traditional to Roth IRA at the same custodian.
- Tax due: with no pre-tax IRA balance left, basis percentage is 100; 0 USD of the conversion is taxable.
- File Form 8606: Part I line 1 = 7,000 USD basis; Part II reports the conversion with zero taxable amount.
2026 Roth IRA income limits and contribution rules
Source: IRS Notice 2025-79 (November 2025) and IRC Section 408A. The phase-out is linear; the calculator computes the partial direct contribution if MAGI falls inside the range.
| Filing status | Full Roth MAGI | Phase-out range | Backdoor needed | 2026 cap |
|---|---|---|---|---|
| Single / HoH | Under 150,000 USD | 150,000 to 165,000 USD | Above 165,000 USD | 7,000 USD (8,000 at 50+) |
| Married filing jointly | Under 236,000 USD | 236,000 to 246,000 USD | Above 246,000 USD | 7,000 USD each (8,000 at 50+) |
| Married filing separately | Zero MAGI threshold | 0 to 10,000 USD | Above 10,000 USD | Backdoor effectively always |
| Mega backdoor (after-tax 401k) | No income limit | N/A | Plan must support it | Up to ~46,500 USD if plan allows |
Common mistakes
- Ignoring the pro-rata rule. The most common failure mode: contribute 7,000 USD, convert, then discover 80 percent of the conversion is taxable because of an old rollover IRA. Always check Traditional, SEP, and SIMPLE IRA balances as of December 31 of the conversion year.
- Skipping Form 8606. Without it the IRS treats the entire conversion as taxable. File it every year you contribute non-deductibly, even if the conversion happens in a later year.
- Conversion year mismatch. A January 2026 contribution converted in December 2026 is one calendar year. A 2025 contribution made in April 2026 still belongs on the 2025 Form 8606 even if converted in 2026.
- Earning interest before conversion. A 7,000 USD contribution earning 12 USD of money market interest creates a 12 USD taxable conversion. Convert quickly to keep Form 8606 clean.
- Forgetting the spouse. Each spouse has their own 7,000 USD cap. A working spouse can fund a non-working spouse's IRA via a spousal contribution. Pro-rata is per individual, not per couple.
- Missing the SEP IRA trap. Self employed contractors with a SEP IRA are pro-rata exposed. Switch to a Solo 401(k) (no IRA balance, no pro-rata) before doing the backdoor.
Related tools and glossary
Frequently asked questions
Is the backdoor Roth legal in 2026?
Yes. The IRS Joint Committee on Taxation acknowledged the strategy in its 2018 Bluebook for the Tax Cuts and Jobs Act, and no statutory limit has been enacted since. The Build Back Better Act of 2021 would have closed it but never became law. As of the 2026 tax year the technique remains explicitly available and widely used.
What is the pro-rata rule and how does it ruin a backdoor Roth?
If you hold any pre-tax balance in any Traditional, SEP, or SIMPLE IRA on December 31 of the conversion year, IRC Section 408(d)(2) treats your conversion as a pro-rata mix of basis and pre-tax dollars. A 7,000 USD non-deductible contribution plus a 93,000 USD pre-tax rollover IRA means only 7 percent of the conversion is tax free; 93 percent is taxed at your marginal rate. The fix is to roll the pre-tax balance into a 401(k) before December 31.
Who needs the backdoor Roth in 2026?
Single filers with MAGI above 165,000 USD or MFJ above 246,000 USD in 2026 cannot make any direct Roth IRA contribution. The phase-out starts at 150,000 USD single and 236,000 USD MFJ. Below the phase-out start there is no reason to use the backdoor: contribute directly. Above 165,000 USD single the backdoor is the only way to fund a Roth IRA each year.
What is the mega backdoor Roth?
The mega backdoor uses after-tax (not Roth) 401(k) contributions then in-plan conversion or in-service rollover to Roth. The 2026 ceiling is the 415(c) limit of 72,000 USD total contributions (or 80,000 USD at 50+) minus your elective deferral and employer match. A common space is 25,000 to 35,000 USD of after-tax room. Only works if your 401(k) plan supports both after-tax contributions and in-service rollovers.
Sources and further reading
- IRS Notice 2025-79 (November 2025), Roth and Traditional IRA limits for 2026, MAGI phase-out ranges.
- IRC Section 408A(c)(3), the Roth IRA income limit statute, and Section 408A(d)(3) governing conversions.
- IRC Section 408(d)(2), the pro-rata aggregation rule for Traditional IRA distributions and conversions.
- Joint Committee on Taxation (2018) General Explanation of Public Law 115-97 (the TCJA Bluebook), pages 289 to 290 acknowledging backdoor Roth contributions.
- IRS Form 8606 instructions (2025 tax year), basis tracking and conversion reporting.